DESCRIPTION: (Adapted from the Applicant's Abstract.) The proposed studies will use a combined dichotic and free-field stimulation method to examine binaural response properties of single neurons, and determine how these response properties shape their sound location selectivity. Recording sites will be marked to determine if these neurons are anatomically organized with respect to binaural properties or spatial tuning. Radial penetrations through cortical columns will determine the homogeneity of response properties in a single column. The cortical surface will be mapped in two dimensions to determine whether aural types are anatomically segregated, and whether within each aural segregation there exists a finer level of functional organization. Results will be compared with similar studies of the inferior colliculus to study the transformation of response properties and functional organization from the midbrain to cortical level. Functional subdivisions of the cortical 60 kHz region will be injected with retrograde tracers to determine the specificity of connections with cortical and subcortical structures.